Vitamin A (Retinol)
Also known as: Retinol, Retinoic Acid, Beta-Carotene (provitamin A), Retinyl Palmitate
Vitamin A plays a critical role in phototransduction in the retina, where 11-cis-retinal is a chromophore in rhodopsin. It is also involved in maintaining the integrity and function of epithelial tissues, supporting immune cell differentiation and function, and acting as a powerful antioxidant by scavenging free radicals. Retinoic acid, a metabolite of retinol, functions as a hormone-like signalling molecule, regulating gene expression through nuclear retinoic acid receptors (RARs) and retinoid X receptors (RXRs), influencing cell growth, differentiation, and apoptosis.
Last reviewed: 2026-04-22 · 4 indexed studies
Set your location for accurate regulatory status
Saved on this device — no sign-in needed.
Overview
Vitamin A is a fat-soluble vitamin and an essential micronutrient vital for numerous physiological processes, including vision, immune function, reproduction, and cellular communication. It exists in several forms, including preformed vitamin A (retinol, retinyl esters) found in animal products, and provitamin A carotenoids (e.g., beta-carotene) found in plants, which are converted to retinol in the body. Retinol is the active form used by the body.
Mechanism & Function
Retinol · C₂₀H₃₀O — source: PubChem CID 445354
Amber retinyl-palmitate oil. Fat-soluble, light- and oxygen-sensitive.
- Softgel
- Liquid
- Capsule
Softgel is generally preferred for bioavailability or efficacy.
Mechanism of Action
Vitamin A, primarily in its various forms, exerts its effects through several mechanisms. Retinal, specifically 11-cis-retinal, is a crucial component of rhodopsin in the rod cells of the retina, essential for vision in low light. Retinoic acid (RA) acts as a ligand for nuclear retinoic acid receptors (RARs) and retinoid X receptors (RXRs), forming heterodimers that bind to specific DNA sequences (retinoic acid response elements) to modulate gene transcription. This gene regulation impacts cell differentiation, proliferation, and immune responses. Additionally, vitamin A metabolites contribute to maintaining epithelial tissue integrity and act as antioxidants.
Physiological Role
Vitamin A is fundamentally involved in vision, particularly night vision, as a component of rhodopsin in the retina. It supports immune system function by influencing the development and differentiation of various immune cells (e.g., T-cells, B-cells) and maintaining mucosal barriers. Furthermore, it is crucial for epithelial cell growth and differentiation, ensuring the health of skin, respiratory, gastrointestinal, and genitourinary tracts. It also plays a role in reproduction, embryonic development, and bone growth.
Primary Pathways
Performance / Health Relevance
While not directly enhancing athletic performance in individuals with adequate status, optimal vitamin A levels are crucial for maintaining overall health, immune function, and vision, all of which indirectly support consistent training and performance. Deficiencies can impair immune response and vision, leading to reduced training capacity and increased susceptibility to illness. Its role in epithelial integrity is also relevant for skin barrier function.
Evidence Review
Compare Vitamin A Forms
Full comparison2 vitamin a forms are indexed. Bioavailability, clinical evidence, and best-use cases differ meaningfully between them.
| Form | Evidence |
|---|---|
Vitamin A (Retinol)This page Preformed vitamin A from animal sources (retinyl esters) is highly bioavailable. Provitamin A carotenoids (e.g., beta-carotene) have variable bioavailability depending on food matrix, processing, and individual factors (e.g., genetic variations, fat intake). Conversion efficiency of beta-carotene to retinol is approximately 12:1 by weight (beta-carotene:retinol). | 70/100 |
| Beta-Carotene Bioavailability is enhanced by dietary fat and cooking. Absorption varies significantly among individuals. | 65/100 |
Practical Use & Dosage
- Minimum Effective Dose
- 700 mcg RAE/day (adult females), 900 mcg RAE/day (adult males)
- Optimal Range
- 700-1500 mcg RAE/day
- Upper / Caution Level
- 3000 mcg RAE/day (preformed Vitamin A)
- Timing
- With a meal containing fat due to its fat-soluble nature
- Best Format
- Retinyl palmitate or beta-carotene for general supplementation. Topical retinoids (tretinoin) for skin conditions.
- Bioavailability
- Preformed vitamin A from animal sources (retinyl esters) is highly bioavailable. Provitamin A carotenoids (e.g., beta-carotene) have variable bioavailability depending on food matrix, processing, and individual factors (e.g., genetic variations, fat intake). Conversion efficiency of beta-carotene to retinol is approximately 12:1 by weight (beta-carotene:retinol).
- Absorption Considerations
- Requires dietary fat for optimal absorption. Absorbed in the small intestine, transported via chylomicrons to the liver for storage or distribution. Zinc is also required for vitamin A transport and metabolism.
Safety & Interactions
Side Effects
- •Nausea
- •Vomiting
- •Headache
- •Blurred vision
- •Dizziness
- •Dry skin/peeling
- •Hair loss
- •Liver damage (chronic high doses)
- •Birth defects (in pregnancy with excessive intake)
Contraindications
- Pregnancy (high doses of preformed vitamin A)
- Liver disease
- Chronic kidney disease
Drug Interactions
- •Orlistat (decreases absorption)
- •Retinoids (e.g., isotretinoin, synthetic vitamin A derivatives - increased risk of toxicity)
- •Tetracyclines (increased risk of intracranial hypertension)
- •Cholestyramine (decreases absorption)
Who Should Avoid
- •Pregnant women (excessive intake)
- •Individuals with liver disease
- •People taking other retinoid medications
Monitoring
Monitor liver function and vitamin A levels in individuals on high-dose or long-term supplementation. Pregnant women should strictly adhere to recommended intake and avoid excessive preformed vitamin A.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is Vitamin A (Retinol) typically used or indicated?
Vitamin A (Retinol) is most commonly used for: Vision support, Immune function, Skin health, Antioxidant support. Vitamin A is fundamentally involved in vision, particularly night vision, as a component of rhodopsin in the retina. It supports immune system function by influencing the development and differentiation of various immune cells (e.g., T-cells, B-cells) and maintaining mucosal barriers. Furthermore, it is crucial for epithelial cell growth and differentiation, ensuring the health of skin, respiratory, gastrointestinal, and genitourinary tracts. It also plays a role in reproduction, embryonic development, and bone growth.
How does Vitamin A (Retinol) work?
Vitamin A, primarily in its various forms, exerts its effects through several mechanisms. Retinal, specifically 11-cis-retinal, is a crucial component of rhodopsin in the rod cells of the retina, essential for vision in low light. Retinoic acid (RA) acts as a ligand for nuclear retinoic acid receptors (RARs) and retinoid X receptors (RXRs), forming heterodimers that bind to specific DNA sequences (retinoic acid response elements) to modulate gene transcription. This gene regulation impacts cell differentiation, proliferation, and immune responses. Additionally, vitamin A metabolites contribute to maintaining epithelial tissue integrity and act as antioxidants.
What is the recommended dose of Vitamin A (Retinol)?
The optimal range is 700-1500 mcg RAE/day. with a minimum effective dose of 700 mcg RAE/day (adult females), 900 mcg RAE/day (adult males). Best taken: With a meal containing fat due to its fat-soluble nature. Upper / caution level: 3000 mcg RAE/day (preformed Vitamin A).
What are the side effects of Vitamin A (Retinol)?
Reported side effects include: Nausea; Vomiting; Headache; Blurred vision; Dizziness; Dry skin/peeling; Hair loss; Liver damage (chronic high doses); and Birth defects (in pregnancy with excessive intake). Monitoring: Monitor liver function and vitamin A levels in individuals on high-dose or long-term supplementation. Pregnant women should strictly adhere to recommended intake and avoid excessive preformed vitamin A.
Does Vitamin A (Retinol) interact with medications?
Known or theoretical interactions: Orlistat (decreases absorption); Retinoids (e.g., isotretinoin, synthetic vitamin A derivatives - increased risk of toxicity); Tetracyclines (increased risk of intracranial hypertension); and Cholestyramine (decreases absorption). Always check with a clinician before combining with prescription medication.
Who should avoid Vitamin A (Retinol)?
Vitamin A (Retinol) is generally not recommended for: Pregnant women (excessive intake); Individuals with liver disease; People taking other retinoid medications; Pregnancy (high doses of preformed vitamin A); Liver disease; and Chronic kidney disease.
How strong is the evidence for Vitamin A (Retinol)?
Evidence level: Moderate (overall score 70/100), based on 4 indexed studies on SuppIndex.
Research & References (4)
Vitamin A and the immune system: an overview
This review discusses the critical role of vitamin A and its metabolites in the proper functioning of the immune system, including cellular and humoral immunity. It highlights how vitamin A deficiency impairs immune responses and increases susceptibility to infections.
Vitamin A and the Retina: New Insights into Molecular Mechanisms of Retinoid Homeostasis and Disease
This article reviews the current understanding of vitamin A metabolism in the eye, focusing on the visual cycle and its implications for ocular health and disease. It details the complex interplay of proteins involved in retinoid transport and processing.
The effect of high-dose vitamin A supplementation on the incidence of acute respiratory tract infections in children with vitamin A deficiency: a meta-analysis of randomized controlled trials
This meta-analysis synthesized evidence from RCTs to evaluate the impact of high-dose vitamin A supplementation on acute respiratory tract infections (ARTIs) in vitamin A deficient children.
Retinoids in skin: topical and systemic applications
This review provides a comprehensive overview of the use of retinoids (vitamin A derivatives) in dermatology, discussing their mechanisms of action, efficacy, and safety profiles for various skin conditions, including acne, psoriasis, and photoaging.
Related Ingredients
Other top-rated ingredients in Vitamins.
Vitamin D3
91/100A secosteroid prohormone converted to calcitriol (1,25-dihydroxyvitamin D), functioning as a nuclear hormone receptor ligand regulating >1000 genes.
Vitamin B3 (Niacin)
80/100Niacin is a precursor to nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+), two critical coenzymes involved in over 400 enzymatic reactions in the body. These reactions are central to energy metabolism, DNA repair, and antioxidant defense. Pharmacological doses of nicotinic acid have a well-established role in lowering LDL cholesterol and triglycerides and raising HDL cholesterol, primarily through inhibiting hepatic VLDL synthesis and reducing fatty acid mobilization. Nicotinamide, while also a source of NAD+, does not exert the same hypolipidemic effects but is crucial for various cellular processes and has shown promise in certain dermatological conditions and neurological contexts at higher doses.
Vitamin B9 (L-Methylfolate / 5-MTHF)
75/100L-Methylfolate is the principal circulating form of folate and the only form that can cross the blood-brain barrier. It plays a critical role as a coenzyme in one-carbon metabolism, particularly in the methylation cycle. Its direct bioavailability makes it a preferred supplemental form, especially when addressing folate deficiencies or supporting processes requiring efficient methylation, such as neurotransmitter synthesis and homocysteine regulation. Research indicates its efficacy in supporting mood, cardiovascular health, and cognitive function, particularly in populations with impaired folate metabolism.
Research Overview
Moderate EvidenceCite this ingredient
One-click citation export in APA, MLA, Chicago, BibTeX, or HTML. The URL below is stable and safe to link.
Stable URL
https://thesuppindex.com/ingredients/vitamin-a-retinol
SuppIndex. (2026). Vitamin A (Retinol): Evidence summary, dosage and clinical studies. Retrieved October 23, 2026, from https://thesuppindex.com/ingredients/vitamin-a-retinol
Based on 4 indexed studies · Evidence level: Moderate.
Goal Ratings
Stack Compatibility
Generally safe when stacked with most vitamins and minerals, though high doses should be avoided with other fat-soluble vitamins without professional guidance. Caution advised when combined with other medications affecting fat absorption or liver function. Ensure adequate zinc intake for optimal vitamin A metabolism.